Interesting findings indeed.
That's a good data to have for comparison (you are still using bitthief's build). Can you also see/record the CPU Load (with htop) during the wifi transfer. Is this wpa2 or 3? I think it doesn't matter but just to know.
Would you try qosmio NSS-wifi branch, if you have time to repeat the same tests plus CPU load (should be zero with NSS-wifi). It'll be very good comparison.
If I had suitable 10G equipment, I would test all of the above myself.
And maybe you already saw it but there is another interesting recent commit for the 10G ports firmware.
Although you fully saturated the cable 10G link.